Wireless charging is becoming increasingly popular with mobile devices such as smartphones and tablets. In some examples, wireless power can make recharging a mobile device as seamless as putting down the mobile device on a wireless charging mat or onto a table having an embedded wireless charger, and the like. In operation, wireless charging may employ electromagnetic induction using an electromagnetic field to transfer power from the charger to the smartphone or tablet, or to another type of receiving device. The induction may involve feeding power to a base unit or charging station having an induction coil. This powered induction coil creates an electromagnetic field. When a second induction coil, such as of a receiving device, becomes near, the power will transfer to the receiving device and be converted back into an electrical current in the receiving device. The wirelessly supplied power can activate the receiving device such as in the case of low-power radio-frequency identification (RFID) chips, charge a battery of the receiving device, and so on. Induction chargers generally operate over a short distance and while physical contact between a receiving device and the wireless charger is typically not necessary for induction to function, such contact may be beneficial to advance the wireless power transfer.
In general, this wireless charging employing inductive charging or resonance inductive charging uses an electromagnetic field to transfer energy between two objects through electromagnetic induction. The supply object may be a charging station. Again, energy is sent through an inductive coupling to the receiving object such as an electronics device which can then use that energy to charge batteries or run the electronics device, and the like. As indicated, induction chargers use an induction coil to create an alternating electromagnetic field from within a charging base. A second induction coil in the portable device takes power from the electromagnetic field and converts the power back into electric current to charge a battery of the portable device or to run the portable device, and so forth. The two induction coils in proximity combine to form an electrical transformer. Greater distances between sender and receiver coils can generally be achieved when the inductive charging system uses resonant inductive coupling.
As indicated, wireless inductive charging is gaining popularity for use in consumer rechargeable applications such as cordless power tools, net books, notebooks, smartphones, tablets, and other rechargeable devices. With inductive charging systems, there is potential of charging multiple devices via a single wall outlet, the convenience of having a vehicle charger that is non-contact, and other examples. In general, power is induced through the primary charging coil and a magnetic field is produced which is then received by the secondary coil and converted back into a voltage. Shielding can be added to either coil of the transformer system to direct the field effects, which can be useful in multiple pad charging applications to reduce power cross-talk, for instance. Intelligent features can also be added to these systems, such as communication to determine varying charge levels and intelligent sensing of foreign objects on the charging pad to disable the charger output, and so forth. Lastly, an issue associated with wireless power systems may be limiting exposure of the electromagnetic fields to people.
The same numbers are used throughout the disclosure and the figures to reference like components and features. Numbers in the 100 series refer to features originally found in FIG. 1; numbers in the 200 series refer to features originally found in FIG. 2; and so on.